1. Field of the Invention
The present invention relates to a drive mechanism for driving a movable mirror provided in a camera (e.g., an SLR camera), and in particular to a shock-absorbing mechanism, provided in association with the drive mechanism, for the movable mirror.
2. Description of the Related Art
In SLR cameras, a movable mirror (quick-return mirror) is provided, which is capable of moving up and down; more specifically, capable of rotating between a viewfinder light-guiding position (mirror-down position), in which the movable mirror is positioned in a photographing optical path to reflect incident light emanated from an object (object-emanated light) toward a viewfinder optical system, and a retracted position (mirror-up position), in which the movable mirror is retracted from the photographing optical path to allow the object-emanated light to travel toward a shutter. If the movable mirror bounces (vibrates) due to shock caused upon reaching a rotational limit position such as the viewfinder light-guiding position or the retracted position, this bouncing of the movable mirror makes the image that is viewed through the viewfinder unstable, causing an adverse effect on the viewing performance of the viewfinder. Additionally, in a camera which is structured to lead light from an object to a distance measuring sensor and a photometering sensor via a movable mirror, a precise distance measuring operation or photometering operation cannot be performed during such bouncing of the movable mirror, which restricts continuous photographing performance. Due to such reasons, various shock-absorbing mechanisms which absorb shock of the movable mirror when it rotates to suppress bounce of the movable mirror have been proposed (e.g., Japanese Unexamined Patent Publication No. 2000-13755).
To improve a continuous photographing capability of a camera, it is desirable that the bounce of the movable mirror be reduced by absorption of shock of the movable mirror when the movable mirror rotates to the viewfinder light-guiding position (when a mirror-down operation is performed) and when the movable mirror rotates to the retracted position (when a mirror-up operation is performed). Therefore, movable mirror shock-absorbing mechanisms equipped with a shock-absorbing member for suppressing bounce of the movable mirror at the viewfinder light-guiding position thereof and another shock-absorbing member for suppressing bounce of the movable mirror at the retracted position thereof are known in the art. However, separately providing such two shock-absorbing members that respectively function at two different rotational (angular) positions of the movable mirror has been a cause of increasing the production cost.
In addition, a member, which applies a load on the rotation of the movable mirror in the reverse direction (bouncing direction) upon the movable mirror reaching the viewfinder light-guiding position or the retracted position, only needs to be provided to suppress bounce of the movable mirror. However, if the load exerted on the movable mirror from the bounce-suppressing member is excessively great, this load may interfere with improvement in the operational speed of the movable mirror. Specifically, at an initial stage of the rotation of the movable mirror from a state where the movable mirror is at the viewfinder light-guiding position or the retracted position, rotational resistance tends to be great, and accordingly, it is desirable that loads on the movable mirror be reduced as much as possible.